A plasma power supply circuit includes a DC/DC converter connected to a DC power supply and outputting a DC voltage, a voltage limit circuit limiting an output voltage from the DC/DC converter to a predetermined value, a PJ capacitor connected to an output end of the DC/DC converter and charged with electric energy used to generate a plasma in a discharge space of the spark plug, and a high-voltage switch connected between the PJ capacitor and the DC/DC converter and controlled to switch ON and OFF so that a charge period of the PJ capacitor is controlled according to running conditions of the internal combustion engine. Hence, the plasma ignition device can prevent damage on an electronic component incorporated therein even at the occurrence of a short and lessen damage on the internal combustion engine caused by an erroneous plasma jet ejection, wearing of the spark plug, and power consumption.